Telephone system



March 16 1926. 1,576,747

H. L. HOFFMANN TELEPHONE SYSTEM Filed Dec. 22, 1923 2 Sheets-Sheet 1 /5xLG March 16 1926.

' 1,576,747 H. L. HOFFMANN TELEPHONE SYSTEM Filed Dec. 22, 1925 2Sheets-Sheet 2 fim/ Alfaffmmn M My Patented Mar. 16, 1926.

UNITED STATES arana orries- HENRY L. HOFFMANN, OF EA ST ORANGE, NEVIJERSEY, ASSIG-NOR TO.XVESTERN ELECTRIC COMPANY, INCORPORATED, OF NEWYORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed December 22. 1923. Serial No. 882,198.

To all whom it may concern Be it known that I, HnNnY L. HOFFMANN, acitizen of the United States of America residing at East Orange, in thecounty-0t Essex and State of New Jersey, have invented certain new anduseful Improvements in Telephone Systems, of which the following is afull, clear, concise, and exact description.

This invention relates to telephone exchange systems, and moreparticularly, to

improvements in the trunk circuit for establishing a connection betweenmanual exchanges.

The invention is adapted for use in systems in which calls received at amanual switchboard at one exchange are extended by means out so called Aoperators link cir cuits and trunk lines terminating at another exchangeand from there by means of so called B operators link circuits at thislatter exchange to a desired subscribers line. In such systems a numberof trunk circuits and a number of B operators link circuits are usuallyprovided and any one of the link circuits may be used for extending theconnection to the wanted subscriber by inserting one plug thereof in thejack of a chosen trunk and the other plug in the jack of a wantedsubscriber's line and the B operators telephone set is manuallyconnected to such a link circuit by means of a key. lhe trunk used isordinarily assigned by the aid of a separate call wire circuit extendingbetween the two exchanges which is available for this purpose to theoperators at the two positions.

An object of this invention is to eliminate the use of call wirecircuits to assign trunk lines by the provision of a so called straightforward trunking system embodying means whereby the A operator mayconnect with any one of the trunk lines leading to the exchange in whichthe wanted subseribers line terminates and whereby the B operator mayselect any available link circuit and by manually connecting it to thewanted subscribcrs line automatically extend the connection from theseized trunk line to the wanted subscriber.

Another object is to automatically connect the B operators telephoneequipment with a trunk line the moment it is seized by the A operator.

Another object is to automatically disconpervisory signals between thetwo operators positions for the purpose of controlling the connectionduring the setting up operations as well as during the conversation orat the release of the connection.

Another object'is to automatically ring a wanted subscribers line whenthe connection is completed.

Another object is to provide means whereby it the B operator transfers aconnection from one seized outgoing line to another as, for example,from a line terminating in a supervisory or monitoring board to a lineterminating at a substation, said second line is automatically rung in amanner similar to that in which the first line was called.

To attain these objects in accordance with i one feature of theinvention the incoming trunk lines and the B operators link circuitsterminate in switching devices by means of which any link circuit takenfor use may be automatically associated with the seized trunk line themoment it is manually connected to the wanted subscribers line.

Anotherfeature is the provision of an arrangement including a secondswitching device which is actuated the moment a trunk circuit is seizedby the A operator to connect the B operators telephone equipment withsaid trunkline and a circuit arrangement for automatically disconnectingthis equipment from the trunk line the moment the manual connection tothe wanted subscriber is completed.

Another feature resides in the provision of signaling means whereby theB operator is notified when the trunk circuit has been seized for theextension of a call and when her telephone equipment is connected to ordisconnected from the seized trunk line.

Another feature is the provision of means whereby the B. operator maytest the wanted subscribers line for a busy condition without causingthe selected link circuit to connect with the seized trunk line andwhereby it the subscribers line is busy, she may send a distinctivesignal over the seized trunk line to the A operator to call herattention to this condition.

Another feature is the provision of a signaling means whereby if the Boperator disconnects accidentally or otherwise, the link circuitconnected to the wanted subscribers line before the A operator isdisconnected from the trunk line the B operator is notified in adistinctive manner of this fact.

Another feature is the provision of a signaling means whereby the Boperator receives a distinctive signal if the A operator disconnects herlink circuit from the seized trunk line.

Another featureis the provision of means for ringing the wantedsubscribers l ne automatically when the link circuit is con nected tosuch line and ringing a second subscribers line when the link circuit istransferred thereto while the A operator'is still connected to theseized trunk line and without disconnecting the/link circuit from saidtrunk line.

Another feature of the invention is .the provision of means whereby theA operator receives a distinctive signal if she has connected with atrunk terminating at an unattended B operators position.

One embodiment of the invention is illustrated in the accompanyingdrawings in which Fig. 1 shown an A operators link circuit at one manualexchange; a. manual subscribers line terminating thereat and theterminating end of a trunk line leading to another exchange.

Fig. 2 shows the incoming end of said trunk line in anothermanualexchange and a B operators link circuit and telephone equipmentembodying the features of this invention and also a wanted subscribersline terminating thereat.

Referring now to the drawings a calling subscribers line 1 terminates injack 2 in a manual switchboard and an A operators link circuit may beemployed to connect line 1 with trunk line C teuninating in a jack 16and extending from there to another manual exchange where it may beconnected through the medium of switch to a B operators link circuit D,which link circuit,

in turn, may be connected by means of plug 65 to a jack 66 of a wantedsubscribers line 100. The trunk line C, which may be one out of a groupof similar trunk lines extending between the two exchanges, may beconnected in common with such trunks to the bank terminals of switch 80as shown, and it is understood that these trunks may also be multipledto the the bank terminals of a number of other similar switches and themovable terminals of each switch connected to a separate link circuitsuch as D. Such a group of link circuits may then be located in a manualswitchboard available to a B operator as is the practice where ordinaryB operators link circuits are used. The B operators telephone equipmentshown belowthe dotted line in Fig. 2 is common to thesetrunk linesandlink circuits and may be associated with any one of the trunk linesby means of a common relay arrangement and a switch 60. As theconstruction of the switches 80 and 60 forms no part of this inventionno de tail description will be given except to say that'they may be ofthe well known finder type, the brushes or movable terminals of whichmay be moved in a step-by-stcp fashion. The brushes of switch 80 may bemoved by the stepping magnet 69 and the brushes of the switch 60 may bemoved by means of the stepping magnet 44 and as these switches have nonormal position the brushes will remain on the terminals to which theywere last advanced.

The invention is best understood by describing the setting up ofaconnection between a calling subscribers line 1 and a called subscribersline by means of the arrangement shown in the drawings and such aconnection will now be described.

Assuming that the subscriber on line 1 has initiated a call in theusualmanner and that A operator has answered it by the insertion of plug3 in jack 2 and connected her telephone set to the link circuit A by theoperation of listening key 10 and received from the calling subscriberthe num ber of the wanted subscriber, she proceeds by inserting thecalling plug 15 in a jack such as 16 of any link circuit such as Gleading to the exchange in which the wanted subscribers line 100terminates. It will be observed that it is not necessary for the Aoperator to have any particular trunk line leading to the desiredexchange assigned her, but she may, on the contrary, connect with any ofthe trunks at the moment most conveniently at hand. hen, therefore, aconnection to any one of the trunks is completed as in this case totrunk line C, circuits are established to connect the B operatorstelephone equipment to this selected trunk as follows: The first circuitis completed'from battery at the A operators link circuit, the lowerright hand winding of repeating coil 17, supervisory relay 18, ringcontacts of plug 15 and jack 16, lower left hand winding of repeatingcoil 30, left hand winding of relay 10, upper left hand winding ofrepeating coil 30, tip contacts of jack 16 and plug 15, upper right handwinding of repeating coil 17 to ground. This circuit energizes relay 18to cause the shunting and extinguishment of the supervisory lamp 19 in awell known manner and at the dis tant exchange energizes relay 40. Theoperation of relay 40 establishes a circuit for relays 4.1 and 42 frombattery, armature and contact of relay 10, outer left hand armature andback contact of relay 91, make before break contacts of relay "i'l,winding of relay 41, resistance 77, winding of relay 4-2 to ground.

The operation of relay 42 closes a circuitfor lamp 43 over an obviouscircuit to notify the B operator that a connection is desired, and thisrelay also closes a circuit for the steppin magnet 44 from battery,winding of stepping magnet 44, armature and back contact of this magnet,right hand armature and front contact of relay 42, left hand armatureand back contact of relay 45 to ground. The stepping magnet 42 nowthrough its self-interrupting contacts is caused to vibrate and in thewell known manner in switches of this type advances thereby the brushes50 and 51 in a step-bystep fashion to hunt for the selected trunk line Cand when brush 50 linds the terminal 52 in its contact bank whichrepresents trunk C a circuit is completed from battery at 40 aspreviously traced to the point 53, and from there to terminal '52, brush50, winding of relay 45 to ground. This circuit causes the operation ofrelay 45 and the deenergization of marginal relay as this path to groundfrom the battery of relay 40 is one of less resistance than that throughthe resistance 77 and winding of relay 42. The release of relay causeslamp 43 to be extinguished and the operation of relay 45 causes the lamp46 to be lighted over an obvious circuit, the extinguishing of lamp 43and lighting of lamp 46 indicating to the B operator that the trunk Chas been found, and that her telephone set will presently be connectedthereto.

The release of relay 42 and the operation of relay 45 open the circuitfor the stepping magnet 44; the relay 42 at its right-hand armature andfront contact and relay 45 at its left-hand armature and back contact,causing the magnet 44 to become deenergized and the brushes 50 and 51thereby permitted to come to rest on the contacts corresponding to thetrunk C. The purpose of brush 51 and the corresponding terminals will bedescribed hereinafter. The operation of relay 41 extends at its innerlefthand armature and front contact and at its right-hand armature andfront contact a circuit from trunk C to the inner lower armature andupper armature of relay 47, which relay is momentarilyenergized by acircuit closed by the energiaation of relay 47 as follows: battery,winding of relay 47, armature and back contact of relay 49, lefthandarmature and front contactof relay 45 to ground.

The cnergis'iation of relay 47 extends the leads previously mentionedfrom the trunk (l to a tone producing device which thereby connected tothe A operators telephone set to notify her that the B operators deviceis about to be connected. This tone circuit may be traced as follows:battery, lower right-hand winding of repeating coil 80, winding of relay84, right-hand armature and back contact of relay 91, inner left-handarmature and front contact of relay 41, inner lower armature and frontcontact of relay 4?, through the secondary of the tone producing deviceAT to upper arn'lature and front contact of relay 47, right-handarmature and front contact of relay 41, upper right-hand winding ofrepeating coil 30 to ground, and the repeated circuit through theleft-hand windings of the repeating coil 30, through the trunk C, jack16, plug 15, listening key 10 to the operators telephone set.

As stated this circuit is only maintained for a short interval as theoperation of relay 47 extends an energizing circuit for relay 48 asfollows: battery, upper winding of relay 48, outer lower armature andfront contact of relay 4'7, armature and back contact of relay 49,left-hand armature and front contact of relay 45 to ground. Relay 48 isthereby operated and locks up to ground at relay 45 and at the same timecauses the energization of relay 49 over a circuit from battery, lowerwinding of relay 48, outer lower armature and front contact of thisrelay, vinding of relay 49, left-hand armature and front contact ofrelay 45 to ground, and the operation of relay 49 at its armature andback contact causes the release of relay 47. The release of relay 4'?and the operation of relay 48 now, therefore, removes the tone producingdevice AT from the circuit to the A operators telephone set and extendsthis circuit to the B operators telephone set OT as follows: The relay4-7 at its inner lower armature and back contact and upper armature andback contact and the relay 48 at its inner lower armature and frontcontact and upper armature and front contact. The A. operator onnoticing the tone may therefore immediately transmitto the B operatorthe number of the wanted subscriber and then release her listening key10 and pays no further attention to the connection until it has beenextended or until it is ready for release, of which she will be notifiedeither by distinct signals that the connection has been completed orthat the wanted subscribers line is busy or that the conversationbetween the subscribers is at an end. 7

As soon as the B operator receives the number of the wanted subscribershe procccds to complete the connection as follows: She may select outof a number of link circuits, such as l) any most conveniently at handand test the wanted subscribers line in the usual manner by touching thesleeve of the jack with the tip of the selected plug and thus if thewanted subscriber is busy cause the operation of the usual busy tonedevice SET associated with-her position. If the B operator receives sucha busy tone she will immediately notify the A operator of this-fact bydepressing a key such as 61 or 62 whichever is most C0l1- vcniently athand, one of these keys being located on the righthand side and theother on the left hand side of the position. The depression of one ofthese keys, for example (32, causes busy signal indications to betransmitted to the A operator by the following circuit from battery,armature and front contact of relay 40, winding of relay 91, bankterminal 92 and brush 51 of switch 60, l-rcy 62 to ground. This circuitcauses the operation of relay 91 which now locks up through its owninner left-hand armature and front contact to. ground from the'batteryat relay 4-0. The operation of relay 91 extends the busy signal circuitto the A operators position as follows: from battery, lower right-handwinding of repeating coil 30, windi k of relay 8%, right-hand armatureand front contact of relay 91, key 90, secondary winding of the busytone produc ing device BBT interrupter 93 to ground. This circuitthrough the interrupter 93 causes the alternate operation and release ofrelay 8t which thereby opens and closes at its armature and frontcontact a shunt circuit through the right-hand winding of re layer). Theinclusion of this shunt winding across the conductors of trunk line Ccauses the alternate release and operation of the supervisory relay 18and the consequent flashing of lamp 19 in the well known manner. It willalso be noted that if {the operator has not yet disconnected hertelephone from the link circuit A by the release of listening key 10,she will at this time in addition to the flashing signal also receive abusy tone signal in her receiver as the busy tone producing device BBThas as stated its secondary winding included in the above traced circuitas shown, this arrangement being provided as an additional means for thespeeding up of the service. These signals continue to operate until theA operator removes her plug 15 from the jack 16.

It should also be noted that the B opcrators telephone is immediatelyremoved from the trunk line at the operation of key 62 as the relay 91at its outer left-hand armature and back contact opens the circuit forrelays 4E5 and 41. The release of relay 45 causes the lamp 16 to beextinguished and relays 1-9 and 4:8 to be released, and the release ofrelays Q8 and 49 cause the B operators telephone equipment to bedisconnected from the trunk line C.

On the other hand, in case the wanted subscriber is not busy the Boperator will complete the connection by inserting plug 65 fully intothe jack 66 and thus cause relay 67 to be energized over an obviouscircuit. The operation of relay 67 immediately causes the lighting oflamp 68 over a circuit from battery, armature and back contact of relay94, lamp 68, second lower armature and front contact of relay 67, enterrighthand armature and back contact of relay to ground to indicate tothe B operator that the line is functioning. The operation of this relay67 also causes the finder switch associated with this link circuit D tobegin its hunting operations for the selected trunk line C and to thisend a circuit is completed for the step-by-step magnet 69 as follows:battery, third lower armature and front contact of relay 67, winding ofmagnet ('39,.the armature and back contact of this magnet, innerright-hand armature and back contact of relay 70 and make before breakcontacts of relay 73 to ground. The stepping magnet 69 ope ates in astep-bystep manner by interrupting its own contacts and thus advances inthe well known manner the movable brushes 81, 82 and 83 of the switch 80until the brushes 81 and 82 come in contact with the terminals of trunkC and brush 88 comes in contact with terminal 8%, which latterconnection closes a circuit from battery, at the outer left-handarmature and front contact of relay 41, which it will be remembered wasenergized at the time the trunk circuit C was seized, through thewinding of relay 71, the above mentioned contact 84: and brush 83, lefthand armature and back contact of relay 73,.left-hand winding of relay70 and inner lower armature and front contact of relay 67 to ground.This circuit causes the operation of relays 71 and 70. Relay 71, inoperating, substitutes in this circuit for the battery at the outerleft-hand armature and front contact of relay 11 the battery at relay4:0 and by means of its contacts, opens the holding circuit for relays11 and 15 and thus causes the immediate disconnection of the B operatorstelephone equipment from the trunk line C as previously explained. Theoperation of relay 70, on the other hand, opens at its inner right-handarmature and back contact the circuit for the stepping magnet 69,causing the switch 80 to stop with the brushes 81 and 82 in connectionwith the trunk line C and the brush 83 remaining in Contact with theterminal 84. This relay 70 also causes the operation of relay 73 over acircuit from battery, third lower armature and front contact of relay 67right-hand winding of relay 73 inner right-hand armature andfrontcontact of relay 70, right-hand make-beforebreak con tacts of relay73 to ground, causing relay 73 to lock up over an obvious circuit viaits inner right hand armature and a makebefore-break contact thereof toground, and also over its lefthand armature and front contact and theright-hand winding of relay 70 to ground. Relay 70 being thereby lockedup in series with relay 7 3 to battery of relay an independent of theground at the inner lower armature and front contact of relay 67. Thepurpose of this relay ope 'ation will become apparent as the descriptionproceeds.

It is further noticed that relay 70 opens at its outer right-handarmature and back contact the circuit for the lamp 68 which is therebyGXQlDgUiSllQCl to indicate to the B operator that the link circuit D is'about to be connected to the trunk line C and that automatic ringing ofthe wanted subscriber has been applied as a circuit was completed at theouter right-hand armature and front contact of relay 70 at itsenergization for relay 72 as follows: battery, armature and back contactof ringing relay 7 4i, outer-lower armature and back contact of relay75, winding of relay 72, fourth lower armature and front contact ofrelay 67 outer righthand armature and front contact of relay 70 toground. This circuit causes the operation of relay 7 2 and ringingcurrent is there fore applied from the source 76 through the winding ofringing relay 74, inner lower armature and back contact of relay 7 5,lower arniature and front contact of rglay 7 2, ring contacts of plug 65and jack 66, through the wanted subscribers bell, back through the tipcontacts of jack 66 and plug 65, upper armature and front contact ofrelay 67, upper armature and front contact of relay 72, upper armatureand back contact of relay 7 5 to ground. When the called subscriberanswers in the usual manner by lifting his receiver from the hook, relay74 operates and disconnects the battery at its armature and back contactfrom the circuit for relay 7 2, which now receives a substitute batterythrough the winding of relay 7 5 formerly shunted by'the first mentionedbattery, causing relay 7 5 to operate to open the ringing circuit at itsupper armature and back contact and inner lower armature and backcontact and substituting therefor at its upper armature and frontcontact and inner lower armature and front contact the leads connectingthe brushes 81 and 82 with the conductors of the trunk line C. Thecalling subscriber at station 1 is now, therefore, connected through tothe called subs scriber and conversation may take place. The A operatoris notified of this fact by the opcratipn of relay 841. the n'lomentrelay 75 is operated, as relay 8% in operating causes the right-handwinding of relay l 'to be shunted across the conductors of the trunk Cto operate relay l8 and extinguish lamp 19.

'lll'ierelease of the connection may be initiated by either subscriberreplacing his receiver on the hook If the calling subscriber hangs uplamp will be lighted or if the called subscriber hangs up lamp 19 willbe lighted by the release of relay 84 in the well known manner. Ineither case it is the duty of the A operator to release the connectionby removing the plugs 3 and from jacks 2 and 16, respectively, and whenthe trunk line C is thus released relay 40 is released, causing therelease of relays 71 and 7 O which as previously explained were heldoperated by the battery at the contacts of relay 40. Relay 70, inreleasing, causes the release of relays 72 and 75, thus opening theconnection of the link circuit to the trunk line C. The release of relay7 also causes lamp 68 to be lighted to maintain a steady glow by closinga circuit at the outer right-hand armature and back contact to groundfor this lamp from battery at the armature and back contact of relay 94-if the wanted subscriber has in the meantime hung up his receiver, thusnotifying the B operator that the A operator has released the connectionand the B operator will now remove. her plug from jack 66, thusreleasing relay 67, extinguishing the lamp 68 and releasing relay 73.

On the other hand if the called subscriber has not replaced hisreceiver, the B operator will be apprised to remove plug 65 from jack 66as follows: Relay 94 will be operated when relay 72 is released by a.cir cuit from battery through its right-hand winding lower armature andback contact of relay 72 through the called subscribers loop back to theupper armature and back contact of relay 72 left hand winding of relay94; to ground, and thus connect the interrupter 96 to the circuit forlamp 68 which will then indicate this fact to the B operator by aflashing signal. Should the subscriber at this moment and prior to theremoval of plug 65 from jack 66 by the B operator, notice that he hadbeen disconnected, desire to reestablish the connection he will move hisreceiver up and down and thus alternately cause the lamp 68 to flash orburn with a steady glow and thus indicate to the B operator that hedesires the connection to be reestablished.

In case of accidental removal of plug 65 from jack 66 before either ofthe subscribers desires a connection to be, released, the signal 68 isautomatically flashed to indicate this fact to the B operatoras-follows: Relay 67 is released whereas relay 78 is still held operatedby the holding circuit from battery at relay 40 and a circuit for thelamp 68' is, therefore, completed from bill)" tery armature and backcontact of relay 94:, lamp 68, second lower armature and back contact ofrelay 67, outer right-hand armature and front contact of relay 73,interrupter 76 to ground. When the B operator receives this flashingsignal she in1- mediately again inserts the plug 65 in jack 66 and thusrestores the connectioi'i her ma l The releas'e'o'f relay 67 in thiscase will also cause'the temporary release of relays 72 and 75 asthecircuit for these relays are controlled by the fourth lower armature and"front contact of relay 67 and ifthe subscriber 100had'inthe meantimehun n) his receiver he would a- 'ain be c l 7 t:

called by the connection of the ringing:

In otherwords, the arrangement is such that the plug i65 can betransferred from 0116"]21Ck to another and the ringing operationsrepe'atedeach timeto' call the *party'uponthe line connected withat themoment.

An arrangement is also "provided whereby in case the B operatorsposition'has to be left unattended, a signal is transmittedto the A"operators position when she has seized the trunk leading tothisoperators position, and to this end key may be depressed and lockedto'connect the busy tonedevice OBT to thesei'zed trunk. hen, therefore,a trunk C is seized, switch 60 operates, as herein'b'efo're' described,to find the 'B operators equipment, but instead of functioning toconnect her telephone set, the relay '91 operatesoveraclrcuit froinbattery, armature and front contact of relay 40, winding ofrelay 91,stationary terminal 92, movable terminal51, lower operatedcontacts ofkey 90'to ground, and relay'91 is thereby locked up from battery atrelay 40 through its innerleft hand armature and front contact toground. The-operation of relay 91 breaks at theouter left hand arma tureand back contact the energizing circuit for relays 42 and 45, preventingthe B operators telephone set from being co nectedto the seized trunk,and by the operation of its'right hand armatureand front contact'closesa circuit for the busy tone device OBT asfollows: from battery, lowerright hand winding of repeating coil 30, wi'ndingcof relay 84, righthand armature andifr-ont contact of relay 9 1,,u-pper operated-contactsof key 90, secondary" winding of the busy tone. device OBT to ground.The busy tone is thus transmitted to the repeating coil 30 and repeatedto the A operator's telephone set over a circuit, as previouslydescribed, to indicate to the A operator that the B operators positionis unattended. When the A operator disconnects her plug 15 from theseized trunk jack 16, relays 40 and 91' are'releas-ed;

What is claimed is:

1. A telephone'systeni comprising. trunk lines, an'operatorstelephoneset, a first subscribers line, means responsive to the connection ofsaid first subscribers line to any one of said trunks to connect'th-eopcratoifs telephone set thereto, a second subscribers line, a linkcircuit for connecting to said second subscribers line, and meansoperative upon the connection of said link circuit to said secondsubscribers line to connect said link circuit tothe said trunk circuit."

2. A telephone system comprising trunk lines, an'operators telephoneset, a calling line, means for connecting any one of said trunks to saidcalling line, an electromagnetic means operative when a trunk is seizedto connect the operators telephone setthereto, other subscribers lines,a'link circuit'for connectingwith any one ofsaid other subv scriberslines, and a secondelectromagnetic means operative responsive to theconnection of said link circuit to one of said other sul scriber's linesfor connecting the link circuit to the trunk line.

3. A telephonesyst'em" comprising trunk lines, anopera-torstelephoneset, means for seizing any one of said trunks, a finder switchresponsive thereto for connecting the operato'rs telephone set to theseized'trunk, subscribers lines, a'link'cir'cuit for connecting'with'any one of said subscribers lines, and a secondfinde'rswitchresponsive to the seizin'gj'of a subscribers" line by the link circuitand the seizure of the trunk line for connectingthe link circuit-to thetrunk line.

4:. A 'telephone'system comprising trunk lines, an operators telephoneset, means for seizing any one of saidtrunks, automatically operatedmeans responsive thereto for connecting the operators telephone set tothe seizedt'runk, subscribers lines, a link circuit forconnecting withany one of said subscribers lines, and a second automaticallyoperate'dmeans responsive to the seizure of the subscribers linebythelink circuit and the seizure ofthetrunk circuit for associatingthelinkcircuit with the seized trunk line;

5. A telephone system comprising trunk lines, an operators telephoneset, a first sub scribers-line, means for connecting any one of saidtrunks to said first subscribers line, means for automaticallyconnecting the op erators telephone set to a trunk line whensaid'trunk'line is so seized, subscribers lines, a link circuit forconnecting with any one of said subscribers lines, means forautomatically connecting the link circuit to said seized trunk line whenthe link circuit has seized-a subscribers line;

6. A' telephone system comprising. trunk lines terminating at one end injacks, a-link circuit having a plug adapted for connection aware? withthe jack of any one of said trunk lines, an automatic switch in whichthe other end of said trunk lines terminate, a second link circuittern'iinatmg at one end in said switch and at the other end in a plug,subscribers lines having -jacks for the connection with the plug out thelink circuit, an operators telephone equipment, means including a switchfor connecting automatically the operators telephone equipment with atrunk line having been seized by said first mentioned link circuit, andmeans associated with said second link circuit for operating said firstmentioned switch to connect this link circuit with said seized trunkline when said link circuit has seized a subscribers line.

7. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks with said first subscribers line, means operative when a trunk isso seized to connect the operators telephone set thereto, othersubscribers lines, a link circuit for connecting with any one of saidother subscribers lines, means operative responsive to the connection ofsaid link circuit to one of said other subscribers lines to connect thelink circuit with said trunk line, and means operative when said othersubscribers line is seized for disconnecting the operators telephone setfrom the seized trunk line.

8. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks to said first subscribers line, means operative when a trunk isso seized to connect the operators telephone set thereto, othersubscribers lines, a link circuit for connecting with any one of saidother subscribers lines, means operative responsive to the connection ofsaid link circuit to one of said other subscribers lines to connect thelink circuit with the trunk line, and means operated when the linkcircuit is connected to the seized trunk line to disconnect theoperators telephone set therefrom.

9. A telephone system comprising trunk lines, an operatoi."s telephoneset, a first subscribers line, means for connecting any one o't saidtrunks with said first subscribers line, means operative when a trunk isso seized to connect the operators telephone set thereto, means toindicate the seizure of a trunk, other subscribers lines, a link circuitfor connecting with any one o't said other subscribers lines, and meansoperative responsive to the connection of said link circuit to one ofsaid other subscribers lines to connect the link circuit with the trunkline.

i0. A telephone system comprising trunk lines, an operators telephoneset, a first sub scribers line, means for connecting); any one of saidtrunks with said first subscribers line, means operative when a trunk isso seized to connect the operatofis telephone set thereto, a signalingmeans operated in response to the connection oi an operators telephoneto the seized trunk, other subscribers lines, a link circuit connectedwith any one of said other subscribers lines, and means operativeresponsive to the connection of said link circuit with one of said othersubscribers lines to connect the link circuit with the trunk line.

11. A telephone system comprising trunk lines, an operators position atone end of said trunks, a first subscribers line terminating at saidposition, an operators position at the other end of said trunks, meansat the first mentioned operators position for connecting any one of saidtrunks, means operative when a trunk is seized to connect the secondmentioned operators telephone equipment thereto, means for indicating tothe first mentioned operator when the second mentioned operatorsequipment is associated with the seized trunk, other subscribers lines,a link circuit at the second operators position for connecting with anyone of said other subscribers lines, and means operated responsive tothe connection of said link circuit to one of said othersubscribers"lines to connect the link circuit with said trunk line.

12. A telephone system comprising trunk lines, an operators position atone end of said trunks, an operators position at the other end of saidtrunks, means at the first mentioned operators position for seizing anyone of said trunks, means operative when a trunk is seized forconnecting the second mentioned operators telephone equipmentt'hereto, ameans operated in response to the connection of the second mentionedoperators equipment to the seized trunk to transmit a momentary signalto the first mentioned operators position over said seized trunk,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, and means operative when a trunk line and asnhscribeids line are seized to connect the link circuit with the trunkline.

13. A telephone system comprising trunk lines, an operatofls position atone end o't said trunks, an operatofls position at the other end of saidtrunks, means at the first mentioned operations position or seizing anyone of said trunks with said first sul scribers line, means operativeupon the seizure of said trunk to connect the second mentioned o1jeratoi"s telephone set thereto, a signaling means associated momentarilywith a trunk when it is seized to transmit to the first mentionedoperators position an audible signal to indicate that the secondmentioned oierators telephone set is about to be connected therewith,subscribers lines,

a link circuit for connecting with any one of said subscribers lines,and means operative when the trunk line and a subscribers line areseized to connect the link circuit with the trunk line.

let. A telephone system comprising trunk lines, an operators position atone end of said trunks, an operators position at the other end of saidtrunks, means at the first mentioned operators position for seizing anyone of said trunks, means operative when a trunk is seized to connectthe second mentioned operators equipment thereto, a signaling meansassociated with the trunkin response to its seizure to transmit to thefirst mentioned operators position an audible signal and disassociatedfrom the trunk when the second n'icntioned operators equip ment isconnected to said seized trunk, sub scribcrs lines, a link circuit forconnecting with any one of said subscribers lines, and means operativewhen the trunk line and a subscribers line are seized to connect thelink circuitwith the trunk line.

15. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one or said trunks, means operative when atrunk is seized to connect the operators telephone set, thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative responsive to the seizure of saidtrunk line andsaid subscribers line to connect the link circuit with thetrunk line, and means associated with the link circuit operative whenthe subscribers line is seized to indicate to the operator that thesubscribers line is not otherwise engaged.

16. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means opera tive' when the trunk line and asubscribers line are seized to connect the link circuit with the trunkline, and a visual signal in said link circuit operated when asubscribers line is seized to indicate that the subscribers line is nototherwise engaged.

17. A telephone system, comprising trunk lines, an operators telephoneset, means for seizing any one of said. trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means open ative when the trunk line and asubscribers line are seized to connect the link circuit with the trunkline, and a visual signal in said link circuit operated when asubscribers line is seized and before the trunk line is connected to thelink circuit.

18-. A. telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, meansfor disconnecting the link circuit from a trunk line when said trunkline is released, and signaling means operative when a link circuit isreleased to indicate to the operator that such a release has takenplace.

19. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with an y one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, meansfor disconnecting the link circuit from a trunk line when said trunkline is released, anda signal intermittently operated when the linkcircuit is released.

20. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunkis seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and anindicating means operative when the link circuit is disconnected fromthe subscribers line but still connected to the seized trunk line.

21. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operations telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and anintermittently operated signal actuated when the link circuit isdisconnected from the subscriliiers line but still connected to theseized trunk line.

22, as telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and anintermittently operated. visual. signal actuated when the link circuitis disconnected from the subscribers line but still connected to theseized trunk line.

23. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means op erative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, meansfor indieating to the operator when a subscribers line is busy, andmeans under control of the operator for transmitting a signal over theseized trunk line to indicate at the opposite end thereof that asubscribers line is busy.

24. A telephone system comprising trunk lines, an operators position atone end of the trunk line, an operators position at the other end ofsaid trunk line, means at the first operators position for seizing anyone of said trunk lines, means operative when a trunk line is seized toconnect the second operators equipment thereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines,means operative when the trunk line and a subscribers line are seized toconnect the link circuit to the trunk line, means for testing asubscribers line as to its busy condition without causing the connectionof the link circuit with the seized trunk line, and signaling meansunder the control of the second operator for notifying the firstoperator that a subscribers line is busy.

25. A telephone system comprising trunk lines, an operators position atone end oi. said trunk line, an operators position at the other end ofsaid trunk line, means at the first operators position for seizing anyone of said trunk lines, means operative when a trunk line is seized toconnect the second operators equipment thereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines,means operative when the trunk line and a subscribers line are seized toconnect'the link circuit with the trunk line, means for testing asubscribers line as to 1ts busy condition without causing the connectionof the link circuit with the seized trunk line, a signaling meanscomprising a device for transmitting a tone, a device for simultaneouslytransmitting an interrupted signal and a key under the control of thesecond operator, to notify the first operator that a subscribers line isbusy.

26. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized-to connect the operators telephone setthereto,subscribers lines, alink circuit for connecting with any one of saidsubscribers lines, means 'erator for operative when the trunk line and asubscribers line are seized to 7 connect the link circuit with the trunkline, means for indicating to the operator when a subscribers line isbusy, and means under the control of the operator for transmitting asignal over the seized trunk line to indicate at the opposite end of thetrunk line that a subscribers line is busy and for disconnectmg theoperators telephone set from the seized trunk. Y

27. A telephone system comprising trunk lmes, an operators position atone end of the trunk lines, an operators position at the other end ofsaid trunk lines, means at the first operators position for seizing anyone or said trunk lines, means operative when a trunk line is seized toconnect the second operators equipment thereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines,means operative when a trunk line and a subscribers line are'seized toconnect the link circuit with the trunk line, means for testing asubscribers line as to its busy condition without causing the connectionof the link circuit with the seized trunk line, signaling means undercontrol of the second operator for notifying the first operator that asubscribers line isbusy, and means under control of the secondopdisconnecting her telephone equipment from the seized trunk line simultaneously with the operation of the said signaling means.

28. A telephone system comprising trunk lines, an operators position atone end of said trunk line, an operators position at the other end ofsaid trunk lines, means at the first operators position' for seizing anyone of said trunk lines, means operative when a trunk line is seized toconnect the second operators equipment thereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines,means operative when the trunk line and a subscribers line are seized toconnect the link circuit with a trunk line, and means at the secondoperators position to prevent the connection of her equipment to theseized trunk line and to transmit a signal to the first operatorsposition over said trunk line to indicate that said second operatorsposition is unattended.

29. A telephone system comprising trunk lines, an operators position atone end of said trunk lines, an operators position at the other end ofsaid trunk lines, means at the first operators position for seizing anyone of said trunk lines, means operative when a trunk line is seized toconnect the second operators equipment thereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines,means operative when a trunk line and a sub scribers line are seized toconnect the link circuit with the trunk line, means including a tonetransmitting device an automatic switching means and a key forconnecting the device to the seized trunk and for transmitting a tone tothe first operators position to indicate that a second operatorsposition is unattended and a means operated by said last mentioned meansto prevent the second operators equipment from being connected with theseized trunk.

30. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative responsive to the connection of saidlink circuitto one of said subscribers lines to connect the link circuitwith said trunk circuit, and means responsive thereto for antomaticallyringing the seized subscribers line.

31. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative responsive to the connection of saidlink circuit to one of said subscribers circuits to connect the linkcircuit with said trunk circuit, and means responsive thereto forautomatically ringing over said seized subscribers line, and forauton'iatically reringing over a second subscribers line if the linkcircuit is transferred thereto from the first subscriber-7s line and notdisconnected from the seized trunk.

32. A telephone system comprising trunk lines, an operator's telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators set thereto, subscribers lines,a link circuit for connecting with any one of said subscribers lines,means operative when the trunk line and a subscribers line are seized toconnect the link circuit with the trunk line, means for disconnectingthe link circuit from the trunk line when it is no longer seized, andsignaling means operative to give a distinctive signal indication whenthe link circuit is no longer connected to the trunk line. and anotherdistinctive signal when the subscriber on the connected subs'cribersline hangs up his receiver.

In witness whereof, I hereunto subscribe my name this 17th day ofDecember A. 1)., 1923.

HENRY L. HOFFMANN.

DISCLAIMER 1,576,747.Henry L. Hofimarm, East Orange, N. J. TELEPHONESYSTEM. Patent dated March 16, 1926. Disclaimer filed October 16, 1929,by the assignee, Western Electric Company, Incorporated.

Hereby enters this disclaimer to the said claims of said Letters Patentwhich are in the following words to wit:

1. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers-line, means responsive to the connection ofsaid first subscribers line to any one of said trunks to connect theoperators telephone set thereto, a second subscribers line, a linkcircuit for connecting to said second subscribers line, and meansoperative upon the connection of said link circuit to said secondsubscribers line to connect said link circuit to the said trunk circuit.

2. A telephone system comprising trunk lines, an operators telephoneset, a

calling line, means for connecting any one of said trunks to saidcalling line, an electromagnetic means operative when a trunk is seizedto connect the operators telephone set thereto, other subscribers lines,a link circuit for connecting with any one of said other subscriberslines, and a second electromagnetic means operative responsive to theconnection of said link circuit to one of said other subscribers linesfor connecting the link circuit to the trunk line.

4. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, automatically operatedmeans responsive thereto for connecting the operators telephone set tothe seized trunk, subscribers lines, a link circuit for connecting withany one of said subscribers lines, and a second automatically operatedmeans responsive to the seizure of the subscribers line by the linkcircuit and the seizure of the trunk circuit for associating the linkcircuit with the seized trunk line.

5. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks to said first subscribers line, means for automaticallyconnecting the operators telephone set to a trunk line when said trunkline is so seized, subscribers lines, a link circuit for connecting withany one of said subscribers lines, means for automatically connectingthe link circuit to said seized trunk line when the link circuit hasseized a subscribers inc.

7. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks with said first subscribers line, means operative when a trunk isso seized to connect the operators telephone set thereto, othersubscribers lines, a link circuit for connecting with any one of saidother subscribers lines, means operative responsive to the connection ofsaid link circuit to one of said other subscribers lines to connect thelink circuit with said trunk line, and means operative When said othersubscribers line is seized for disconnecting the operators telephone setfrom the seized trunk line.

8. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks to said first subscribers line, means operative when a trunk isso seized to connect the operators telephone set thereto, othersubscribers lines, a link circuit for connecting with any one of saidother subscribers lines, means operative responsive to the connection ofsaid link circuit to one of said other subscribers lines to connect thelink circuit with the trunk line, and means operated when the linkcircuit is connected to the seized trunk line to disconnect theoperators telephone set therefrom.

9. A telephone system comprising trunk lines, an operators telephoneset, a first subscribers line, means for connecting any one of saidtrunks with said first subscribers line, means operative when a trunk isso seized to connect the operators' telephone set thereto, means toindicate the seizure of a trunk, other subscribers lines, a link circuitfor connecting with any one of said other subscribers lines, and meansoperative responsive to the connection of said link circuit to one ofsaid other subscribers lines to connect the link circuit with the trunkline.

11. A telephone system comprising trunk lines, an operators position atone end of said trunks, a first subscribers line terminating at saidposition, an operators position at the other end of said trunks, meansat the first mentioned operators position for connecting any one of saidtrunks, means operative when a trunk is seized to connect the sec-0ndmentioned operators telephone equipment thereto, means for indicating tothe first mentioned operator when the second mentioned operatorsequipment is associated with the seized trunk, other subscribers lines,a link circuit at the second operators position for connecting with anyone of. said other subscribers lines, and means operated responsive tothe connection of said link fircuit to one of said other subscriberslines to connect the link circuit with said trunk 12. A telephone systemcomprising trunk lines, an operators position at one end of said trunks,an operators position at the other end of said trunks, means at thefirst mentioned operators position for seizing any one of said trunks,means operative when a trunk is seized for connecting the secondmentioned operators telephone equipment thereto, a means operated inresponse to the connection of the second mentioned operators equipmentto the seized trunk to transmit a momentary signal to the firstlnentioned operators position over said seized trunk, subscribers lines,a link circuit for connecting with any one of said subscribers lines,and means operative when a trunk line and a subscribers line are seizedto connect the link circuit with the trunk line.

15. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative responsive to the seizure of saidtrunk line and said subscribers line to connect the link circuit withthe trunk line, and means associated with the link circuit operativewhen the subscribers line is seized to indicate to the operator that thesubscribers line is not otherwise engaged.

16. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and avisual signal in said link circuit operated when a subscribers line isseized to indicate that the subscribers line is not otherwise engaged.

17. A telephone system, comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for con necting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and avisual signal in said link circuit operated when a subscribers line isseized and before the trunk line is connected to the link circuit.

19. A telephone system comprising trunk lines, an operators telephoneset,

means for seizing any one of said trunks, means operative when a trunkis seized to connect the operators telephone set thereto, subscriberslines, a link circuit for connecting with any one of said subscr berslines, means operative when the trunk line and a subscribers line areseized to connect the link circuit with the trunk line, means fordisconnecting the link circuit from a trunk line when said trunk line isreleased, and a signal intermittently operated when the link circuit isreleased.

20. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and anindicating means operative when the link circuit is disconnected fromthe subscribers line but still connected to the seized trunk line.

21. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk inc and a subscribersline are seized to connect the link circuit with the trunk line, and anintermittently operated signal actuated when the link'circuit isdisconnected from the subscribers line but still connected to the seizedtrunk line.

22. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative when the trunk line and a subscribersline are seized to connect the link circuit with the trunk line, and anintermittently operated visual signal actuated when the link circuit isdisconnected from the subscribers line but still connected to the seizedtrunk line.

' 30. A telephone system comprising trunk lines, an operators telephoneset,- means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators telephone set thereto,subscribers lines, a link circuit for connecting with any one of saidsubscribers lines, means operative responsive to the connection of saidlink circuit to one of said subscribers lines to connect the linkcircuit with said trunk circuit, and means responsive thereto forautomatically ringing the seized subscribers line.

32. A telephone system comprising trunk lines, an operators telephoneset, means for seizing any one of said trunks, means operative when atrunk is seized to connect the operators set thereto, subscribers lines,a link circuit for connecting with any one of said subscribers lines,means operative when the trunk line and a subscribers line are seized toconnect the link circuit with the trunk line, means for disconnectingthe link circuit from the trunk line when it is no longer seized, andsignaling means operative to give a distinctive signal indication whenthe link circuit is no longer connected to the trunk line and anotherdistinctive signal when the subscriber on the connected subscribers linehangs up his receiver.

[Oflicial GazetteNovember 5, 1 9219.]

